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1
Introduction
O n August 14, 2003, more than 50 million people across the northeastern
United States and Canada experienced an electrical blackout. While the
blackout was caused not by a fuel shortage but by faulty controls in the
grid, this event underscores the United States dependence on electricity. Munici-
palities faced urgent challenges related to contaminated drinking water, fighting
fires, looting, health care, and transportation services. Train and airline traffic
was canceled, and thousands of passengers were trapped when more than 600
subway and commuter rail cars stopped in the middle of tunnels. Road travel was
also affected as traffic lights stopped functioning, and many gas stations were
unable to pump fuel because there was no electric power. Hundreds of people
were trapped in elevators. Hospitals struggled to treat their most serious patients.
Some areas lost water pressure because pumps did not have power, causing
possible contamination of water supplies. Individuals quickly realized how diffi-
cult simple daily tasks became without electricity, because they could not charge
their cell phones, refrigerate or cook food, ride in elevators, or turn on air condi-
tioning (Answers.com, 2005). It took New York City 29 hours to restore power,
while other areas did not have electricity restored for up to four days. It is
estimated that the economic cost to New York City alone due to the blackout was
more than $500 million (Figure 1.1). Even though Americans depend on electric-
ity for most everyday activities, the majority of people do not realize that electric-
ity is provided primarily by coal-fired electric utilities.
Coal-fired utilities represent the largest single source of electrical generation
in the United States. In 2003, total U.S. coal consumption was nearly 1,095
13

14 MANAGING COAL COMBUSTION RESIDUES IN MINES
FIGURE 1.1 Pedestrians and vehicles clog New York's Brooklyn Bridge, August 14, 2003.
SOURCE: AP, 2003. Courtesy of the Associated Press.
million short tons,1 with the U.S. electric power industry consuming 1,004 mil-
lion short tons of that total (USDOE, EIA, 2003a). The combustion of coal results
in the formation of coal combustion residues (CCRs), the noncombustible portion
of the coal itself and residues from various air pollution control technologies,
such as sulfur dioxide scrubbers, installed at the combustion facility. Specific
examples of CCRs include fly ash, bottom ash, boiler slag, and flue gas desulfu-
rization sludge.
During 2003, the combustion of coal resulted in at least 121 million short
tons of CCRs (USDOE, EIA, 2003b) produced by utilities and an additional 5
million short tons produced by independent power producers firing coal refuse
(PADEP, 2004). This mass is approximately 890 pounds per capita,2 which is
roughly the amount of municipal solid waste disposed in landfills throughout the
United States per capita each year (USEPA, 2005a). To paint a better picture, the
1 The U.S. ton is the short ton, which is equal to 2,000 pounds; the British ton is the long ton,
which is equal to 2,240 pounds (see Glossary for more detail).
2Calculated from 126 million tons divided by the 2003 census population of 283 million.

INTRODUCTION 15
amount of CCRs produced annually would fill about one million standard rail-
road coal cars, which, if hitched together, would create a train about 9,600 miles
long (Conrail Cyclopedia, 2005) that would span the United States from New
York City, New York, to Los Angeles, California, 3.5 times.
The management of large volumes of CCRs is a challenge for utilities, be-
cause they must either place the CCRs in landfills, surface impoundments, or
mines, or find alternative uses and markets for the material, such as the use of fly
ash in concrete production. Each of these methods for disposing of CCRs has
advantages and disadvantages pertaining to various factors including cost and
environmental risk. To meet their CCR disposal needs, utilities often, as part of
their contractual relationship with coal suppliers, require that a mine take the
CCRs for use in reclamation, the process by which land-use capability is restored
at a mine site.
This report examines the management, benefits, and health and environmen-
tal risks associated with the placement of CCRs in active and abandoned coal
mines. To begin, this chapter provides an introduction to coal mining and CCRs
to set the stage for the more in-depth discussion of CCRs and their placement in
mines in the following chapters. This introduction briefly reviews coal produc-
tion and use in the United States, including where and how coal is mined; man-
agement of CCRs, including how they are produced and disposed of; and the
purpose of this study.
COAL PRODUCTION AND USE IN THE UNITED STATES
Coal is the world's most abundant fossil fuel and the largest single source of
fuel for electricity production in the United States (Sidebar 1.1). More than 90
percent (USDOE, EIA, 2003a) of the coal mined in the United States is used by
SIDEBAR 1.1
Geological Origin of Coal
Coal is a fossil fuel formed from the remains of organic plants that existed
millions of years ago. The plant matter was buried by sediment, and the weight of
these overlying deposits compacted the buried plant organic matter. Heat, pres-
sure, and chemical and physical changes took place while the plant matter was
buried, driving oxygen out of it and leaving rich hydrocarbon deposits. Through this
process, the plant matter was gradually transformed into coal. Coal has a highly
variable composition, affecting both its chemical and its physical properties. It may
contain significant amounts of sulfur, arsenic, and other materials that can lead to
environmental concerns as the coal residue is produced.
SOURCES: Rice et al., 1979; Hoffman, 2002.

16 MANAGING COAL COMBUSTION RESIDUES IN MINES
Petroleum
and Other
Sources
(4.7%)
Nuclear
(20.5%)
Coal (52.5%)
Natural Gas
(15.3%)
Hydroelectric
(7.1%)
FIGURE 1.2 Electricity generation in the United States, showing proportion generated
by energy source, 2003.
SOURCE: USDOE, EIA, 2004a.
commercial power plants to generate electricity. In 2003, 1,004 million short tons
of coal generated more than 50 percent of all the electric power produced in the
United States (Figure 1.2; USDOE, EIA, 2004a). In 2003, coal consumption for
electricity production increased by 2.7 percent (USDOE, EIA, 2003a, 2004a),
and the percentage of electricity produced from coal is expected to increase
through 2025 (Figure 1.3).
Coal has a highly variable composition affecting both its physical and chemi-
cal properties. Four types of coal and coal refuse (called culm when derived from
anthracite mines and gob when derived from bituminous mines) with widely vary-
ing characteristics are used in the production of electricity and heat (Table 1.1).
The United States has approximately 25 percent of the world's coal reserves
(USDOE, EIA, 2004b). More than 400 coalfields and small deposits cover a total
of 458,600 square miles in 38 states, split nearly evenly between the eastern and
western United States (Figure 1.4; Chircop, 1999). Although approximately 300
different coal deposits are mined each year, almost 47 percent of total production
comes from just 10 of the largest deposits. In 2003, 51 percent of the country's
total coal production of 1,071.8 million short tons came from western mines, 36
percent from the Appalachian area, 13 percent from Midwest area mines, and less
than 1 percent from coal refuse recovery (USDOE, EIA, 2003a).

INTRODUCTION 19
In 2003, 1,316 mines were actively operating in the United States. Of these,
approximately 67 percent were surface mines and the remaining were under-
ground mines (USDOE, EIA, 2003c). Surface mining is used when coal is found
close to the surface and involves removing the topsoil, the subsoil, and other rock
units, called overburden, and setting them aside. After the coal is removed, the
area is reclaimed, refilled with the overburden, and covered with the soils that
were saved; then the land is reshaped and reseeded. Underground mining is used
to extract coal that lies deep beneath the surface; an underground mine's coal is
removed mechanically and transferred by shuttle car or conveyor to the surface.
Besides utilities, other industries and manufacturing plants use coal. Steel
production accounts for the second largest use of coal; coal is placed in hot
furnaces to produce coke, a form of coal that is used to smelt iron ore for making
steel. Other industries use coal directly for the production of chemicals, cement,
paper, ceramics, and various metal products. Coal is also an ingredient in prod-
ucts such as plastics, tar, synthetic fibers, fertilizers, medicines, dyes, paint, dis-
infectants, shampoo, soap, detergents, and cosmetics (University of Pittsburgh,
2000; Solid Energy, 2002; Cosmetics Programme, 2005; USDOE, EIA, 2005b).
MANAGEMENT OF COAL COMBUSTION RESIDUES
The combustion of coal produces heat. The heat is used to make steam that is
then used to drive electrical generators or perform other types of steam-driven
work. The combustion of coal also generates various forms of solid residues,
including fly ash, bottom ash, boiler slag, and flue gas desulfurization sludge.
These materials are known by a variety of terms including coal combustion
waste, coal combustion product, fossil fuel combustion waste, coal combustion
material, coal combustion ash, coal combustion by-product, and coal combustion
residue. For the purpose of this report the committee chose to use the term "coal
combustion residue." This term was chosen to avoid implying that these materi-
als are destined for particular fates. The characteristics of CCRs are influenced by
several factors such as the source coal, combustion technology, and power plant
air pollution control technology. The characteristics of CCRs are discussed in
more detail in Chapter 2.
Burning coal and coal refuse to generate electricity produced more than 120
million short tons of CCRs in 2003 (USDOE, EIA, 2003c; PADEP, 2004). The
amount will likely increase as the demand for coal-based energy in the United
States grows and as air pollution control technology is more widely used for
capturing residues. Utilities dispose of CCRs by placing them in landfills, surface
impoundments, or mines (Sidebar 1.2 and Figure 1.5) or by finding alternative
uses and markets for the material. Alternative uses for CCRs can include the
production of concrete, wallboard, filler for paint and other products, and manu-
facturing of mortars (ACAA, 2005b). Of the approximately 126 million short
tons of CCRs reported to have been produced in 2003, 46 million short tons (37

20 MANAGING COAL COMBUSTION RESIDUES IN MINES
SIDEBAR 1.2
Placement Options
In 1999, it was estimated that approximately 600 fossil fuel combustion waste
management units, defined by the Environmental Protection Agency (EPA) as
landfills and surface impoundments, were in operation at approximately 450 coal-
fired utility power plants. At the time, the 600 units included equal proportions of
landfills and surface impoundments, although the trends in 1999 suggested an
increasing preference for landfills (USEPA, 1999a).
Surface impoundments are natural depressions, excavated ponds, or diked
basins that usually contain a mixture of liquids and solids. CCRs managed in sur-
face impoundments typically are sluiced with water from the point of generation to
the impoundment. The solid CCRs gradually settle out of this slurry, accumulating
at the bottom of the impoundment. This process leaves a standing layer of relative-
ly clear water at the surface, which is commonly termed head. Solids that accumu-
late at the bottom of a surface impoundment may be left in place as a method of
disposal. The impoundment also may be dewatered periodically and the solids
removed for disposal elsewhere, such as a landfill (USEPA, 1999a).
Landfills are facilities usually constructed in sections called cells, in which
residues are placed for disposal on land. Residues are placed in the active cell and
compacted until the predetermined cell area is filled. Completed cells are covered
with soil or other material, and then the next cell is opened. Cells constructed on
top of previously completed cells are called lifts. Landfills are usually natural de-
pressions or excavations that are gradually filled with residue, although the con-
struction of lifts may continue to a level well above the natural grade. Coal com-
bustion residues managed in landfills may be transported dry from the point of
generation, or they may be placed after dredging from a surface impoundment.
Residual liquids may be placed along with the dredged solids. Also, liquids may be
added during the construction of the landfill for dust control purposes (USEPA,
1999a).
Minefills involve the placement of CCRs in surface or underground mine voids
(USEPA, 1999a). When used in surface mines, the CCRs are incorporated into the
mine reclamation plan and generally are deposited in the mine as backfill combined
with the overburden or as a monofill. They can be used in mine reclamation to
achieve the approximate original contour. CCRs can also be used to form a grout to
fill underground mines in order to prevent subsidence (USEPA, 2002a). Because
the transportation of CCRs to the disposal site can be costly, disposal in mines is
commonly done when the utility and the mine are located near one another.
percent) went to alternative uses (AACA, 2005a); 73 million short tons (58
percent) were placed by utilities into surface impoundments, landfills, and other
on-site locations (USDOE, EIA, 2003b); and approximately 7 million short tons
(5 percent)--2 million short tons from traditional utilities and 5 million short tons
from independent power producers fueled by coal refuse--were used in mine
applications. According to the American Coal Ash Association Coal Combustion

INTRODUCTION 21
FIGURE 1.5 Coal combustion residue mine placement sites in the United States.
SOURCE: National Research Council; data collected through individual state surveys.
Product Production and Use Survey (2005a), such mine applications may include
use in surface mine reclamation, underground mining projects, and use in other
mining industries such as sand and gravel pits. The available data are likely to
underestimate the actual tonnage of CCRs being placed in coal mines due to
deficiencies and inconsistencies in the current reporting framework (see Chapter
2, Sidebar 2.4).

22 MANAGING COAL COMBUSTION RESIDUES IN MINES
SIDEBAR 1.3
Statement of Task
In response to a request from Congress, the National Research Council con-
ducted a study that examined the health, safety, and environmental risks associat-
ed with using coal combustion wastes (CCWs)a for reclamation in active and aban-
doned coal mines. The study looked at the placement in abandoned and active,
surface and underground coal mines in all major coal basins. The study consid-
ered coal mines receiving large quantities of coal combustion wastes. The commit-
tee focused its efforts on coal combustion wastes from utility power plants and
independent power producers, rather than small business, industries, and institu-
tions. A profile of the utility industry was taken into consideration in designing the
study to focus on the sources producing the greatest quantities of coal combustion
wastes.
Specifically, the committee addressed the following points:
1. The adequacy of data collection from surface-water and groundwater
monitoring points established at CCW sites in mines.
2. The impacts of aquatic life in streams draining CCW placement areas
and the wetlands, lakes, and rivers receiving this drainage.
3. The responses of mine operators and regulators to adverse or unintend-
ed impacts such as the contamination of groundwater and pollution of surface
waters.
4. Whether CCWs and the mines they are being put in are adequately char-
acterized for such placement to ensure that monitoring programs are effective and
groundwater and surface waters are not degraded.
5. Whether there are clear performances standards set and regularly as-
sessed for projects that use CCW for "beneficial purposes" in mines.
PURPOSE OF THE STUDY
Whether CCRs should be placed in coal mines and, if so, under what condi-
tions, are important policy issues. Many CCRs can be recycled for use in engi-
neering applications or products such as cement or wallboard--uses that avoid
other environmental impacts and the consumption of other natural resources. The
remainder must be disposed. Using CCRs in mine reclamation avoids having to
dispose of them in landfills and/or surface impoundments, limiting the environ-
mental disturbance of other land. Concerns have been raised about public health
and environmental risks posed by mine placement of CCRs, especially when they
come in contact with water. Burning coal concentrates metals and metalloids,
such as arsenic, cadmium, chromium, and lead, in the CCRs, compared to the
original coal, and alters the leachability of the contaminants by changing the
mineralogy of the material (USGS, 2002). As an example of the risks to be

INTRODUCTION 23
6. The status of isolation requirements and whether they are needed.
7. The adequacy of monitoring programs including:
a. The status of long-term monitoring and the need for this monitoring after
CCW is placed in abandoned mines and active mines when placement is com-
pleted and bonds released;
b. Whether monitoring is occurring from enough locations;
c. Whether monitoring occurs for relevant constituents in CCW as deter-
mined by characterization of the CCW; and
d. Whether there are clear, enforceable corrective actions standards regu-
larly required in the monitoring.
8. The ability of mines receiving large amounts of CCW to achieve economically-
productive post-mine land uses.
9. The need for upgraded bonding or other mechanisms to assure that ade-
quate resources area available for adequate periods to perform monitoring and
address impacts after CCW placement or disposal operations are completed in
coal mines.
10. The provisions for public involvement in these questions at the permitting
and policy-making levels and any results of that involvement.
11. Evaluation of the risks associated with contamination of water supplies
and the environment from the disposal or placement of coal combustion wastes in
coal mines in the context of the requirements for protection of those resources by
the Resource Conservation and Recovery Act (RCRA) and the Surface Mining
Control and Reclamation Act (SMCRA).
aAlthough the term "coal combustion wastes" (CCWs) was used in the statement
of task, after much discussion the committee chose to use the term "coal com-
bustion residue" (CCR) for the purpose of this report. This term was chosen to
avoid implying that these materials are destined for particular fates.
considered, the Safe Drinking Water Act places limits on the presence of some of
these constituents in public water supplies. The placement of CCRs in coal mines
is a complex issue that involves consideration of possible human health and
environmental impacts, as well as a comparison of the economic, health, and
environmental impacts from other disposal options or uses (see Chapter 4).
CCR mine placement is indirectly regulated under the Surface Mining Con-
trol and Reclamation Act (SMCRA). This act gives states the option of develop-
ing and implementing their own programs, subject to national standards and
federal oversight (see Chapter 5). Thus, at present, regulation of CCR mine
placement is primarily a state issue.
Concern about the potential public health and environmental risks associated
with using CCRs for reclamation in active and abandoned coal mines led Con-
gress to direct the Environmental Protection Agency (EPA) to commission an
independent study to examine this topic. As a result, the National Research

24 MANAGING COAL COMBUSTION RESIDUES IN MINES
Council (NRC) established the Committee on Mine Placement of Coal Combus-
tion Wastes to undertake a study to address issues outlined in the statement of
task (Sidebar 1.3). The committee consists of 14 experts from academia, industry,
and state government with expertise in hydrogeology, geology, geochemistry,
nuclear chemistry, biology, ecology, toxicology, epidemiology, occupational and
environmental medicine, natural resource economics, environmental policy, en-
vironmental law, mining regulations, environmental engineering, mining engi-
neering, geotechnical engineering, and coal mining. Brief biographies of the
committee members appear in Appendix A.
This report is intended for multiple audiences including the general public. It
contains advice for EPA and the Office of Surface Mining (OSM), other federal
agencies, and state regulatory agencies, as well as policy makers, the coal indus-
try, and its consultants, scientists, and engineers.
THE COMMITTEE'S APPROACH
To address the statement of task, the committee reviewed relevant govern-
ment documents and materials, pertinent National Research Council reports, in-
formation submitted to the committee by various sources (see Appendix B), and
other technical reports and literature published through July 2005. In addition, the
committee held seven meetings, six of which included information-gathering
sessions that were open to the public, between October 2004 and August 2005.
The information-gathering sessions included presentations by and discussions
with personnel from EPA, OSM, and other federal, state, and local government
agencies and representatives of industry, academia, environmental organizations,
and citizens' groups (Appendix B). To obtain input from the public, the commit-
tee also held six public testimony sessions, in conjunction with the information-
gathering meetings, in Washington, D.C.; Farmington, New Mexico; the Navajo
Nation, New Mexico; Austin, Texas; Evansville, Indiana; and Harrisburg, Penn-
sylvania. During the information-gathering meetings the committee, subgroups
of the committee, and individual committee members also visited several mine
sites that were currently using or had previously used CCRs for minefilling.
In addition to published technical reports, the committee considered numer-
ous letters and reports (in both final and draft form), data compilations (both
formal and informal materials), and other materials from citizens' groups, indus-
try groups, and state and federal regulatory agencies. The information ranged
from materials dealing with individual mining and CCR disposal sites (a few that
the committee visited, as well as other sites) to compilations of monitoring data
and interpretive reports of monitoring data. Further, at the information-gathering
meetings the committee received public testimony pertaining to more than a
dozen sites where CCR has been placed in mines, including sites where CCR has

INTRODUCTION 25
been implicated in the degradation of environmental quality. In total, the commit-
tee heard presentations or received testimony from more than 120 individuals.
The committee considered all of this information during its deliberations.
The information helped to identify data needs, as discussed in more detail later in
this report. The reports and presentations often communicated conflicting views
and interpretations of the environmental impacts of particular sites. Citizens'
groups presented information on environmental degradation (e.g., water quality
contamination) that may be related to CCR placement in mines and/or overall
mining operations. This information was contrary to industry information that
was presented, and many of these presentations were questioned or the interpre-
tations were challenged by state agency personnel. In the committee's review of
these data, it noted not only differences in their interpretation, but in several cases
clear discrepancies in the data themselves. Although these discrepancies were
quite informative, it is well beyond the committee's charge to review and resolve
these local disputes. Hence, these local issues are not discussed in this report. To
the extent possible, the committee has attempted to use and cite independently
peer-reviewed reports and other information and government agency reports that
are typically independently reviewed and available to the scientific community
for review and comment.
In addition, during public testimony, citizens raised concerns about various
public health and environmental issues related to CCRs and mining operations,
such as traffic hazards, fugitive dust, and respiratory problems related to trans-
porting CCRs to mine sites. Although these issues may be important health and
safety concerns for the affected communities, they are beyond the charge and
capability of this committee to address in this report.
Although CCRs have also been placed in other mine settings, including sand
and gravel mines and base metal mines, the committee restricted its consider-
ations to the placement of coal combustion residues in coal mines. Also, some
coal-burning facilities add other combustible materials with coal (e.g., municipal
wastes, old tires, waste oil), and a few mines accept other materials, such as
dredge spoils, for minefill. To stay within its charge, the committee decided to
include only materials derived directly from coal.
Related to its statement of task, the committee also limited its consideration
to the impacts of placing large quantities of CCR in coal mines. With the limited
data directly applicable, the committee did not attempt to evaluate or comment on
possible impacts from relatively small-scale applications of CCRs such as their
use on mine roads. The committee also did not consider occupational safety
issues.
The committee's analysis focuses on the use of CCRs in surface mine recla-
mation, the largest use of CCRs for minefilling. The principles and standards
presented in this report apply to placement of CCRs in underground mines as
well, although such applications are relatively minor.
While the statement of task may not have specified that the committee evalu-

26 MANAGING COAL COMBUSTION RESIDUES IN MINES
ate impacts from the disposal of CCRs in landfills and surface impoundments, or
the recycling of CCRs for other purposes, it was not feasible to address the
impacts of CCR use in minefilling without comparison to other disposal and use
options. Particularly, limitations in data available on the practice necessitated the
review of environmental impact data from landfills and surface impoundments
because these case studies illustrate how CCRs may affect human and environ-
mental health (see Chapter 4).
REPORT ROADMAP
The chapters that follow address the statement of task and present the
committee's findings and recommendations. Chapter 2 describes coal combus-
tion residue production, characteristics, reuse, and placement technologies. Chap-
ter 3 examines the behavior of coal combustion residues in the environment.
Chapter 4 looks at the potential environmental impacts, considerations for human
health, and reasons for concern regarding placement of CCRs in mines (statement
of task numbers 2 and 3). Chapter 5 provides an overview of the regulatory
framework governing the placement of CCRs in mines (statement of task number
5). Chapter 6 discusses the risk management framework for CCR disposal, as
well as material and site characterization and prediction (statement of task num-
ber 4). Chapter 7 addresses site management strategies including reclamation and
monitoring practices (statement of task numbers 1, 6, 7, and 8). Chapter 8 sum-
marizes the committee's overall management approach and other overarching
issues (statement of task numbers 9, 10, and 11). Technical terms and acronyms
are defined in Appendixes C and D.

Burning coal in electric utility plants produces, in addition to power, residues that contain constituents which may be harmful to the environment. The management of large volumes of coal combustion residues (CCRs) is a challenge for utilities, because they must either place the CCRs in landfills, surface impoundments, or mines, or find alternative uses for the material. This study focuses on the placement of CCRs in active and abandoned coal mines. The committee believes that placement of CCRs in mines as part of the reclamation process may be a viable option for the disposal of this material as long as the placement is properly planned and carried out in a manner that avoids significant adverse environmental and health impacts. This report discusses a variety of steps that are involved in planning and managing the use of CCRs as minefills, including an integrated process of CCR characterization and site characterization, management and engineering design of placement activities, and design and implementation of monitoring to reduce the risk of contamination moving from the mine site to the ambient environment. Enforceable federal standards are needed for the disposal of CCRs in minefills to ensure that states have adequate, explicit authority and that they implement minimum safeguards.

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